The prevent invention relates generally to automotive products and, more particularly, to an apparatus for adjusting the toe in the nonsteerable rear wheels of a vehicle having an independent rear wheel suspension system.
In a conventional independent rear suspension system for an automotive vehicle, each rear wheel is mounted independently of the other, i.e. there is no common rear axle. Each rear wheel is rotatably mounted on a wheel spindle which is, in turn, fixedly bolted to the lower end of an elongate, generally vertically extending shock strut. The upper end of the shock strut is attached to a body side panel, typically by a rubber insulated top mount assembly with attachment bolts. Due to the length and resiliency of the shock strut, the spindle and attached tire are, to a small degree, displaceable in a direction perpendicular to the longitudinal axis of the shock strut and are also torsionally (twistably) displaceable about this axis if otherwise unrestrained. In order to restrain this movement and hold the wheel in a fixed orientation with respect to the vehicle frame, a longitudinally extending restraining member, generally referred to as a tie rod, and a pair of laterally extending restraining members, generally referred to as control arms, are affixed at one end to the spindle and at an opposite end to the vehicle frame and body assembly. Due to manufacturing tolerances, etc. in the rear wheel assembly, the "toe" of a rear wheel in some cases needs adjustment. The "toe" a of wheel refers to the angle which the axis of rotation of the wheel makes with a horizontal axis extending perpendicular to the central longitudinal axis of the vehicle, i.e. the amount of angular displacement of the rotation axis from a lateral vehicle axis. When the vehicle toe is properly adjusted, the rotation axis of the wheel should generally be parallel to a lateral vehicle axis. If the front of the wheel is tilted inwardly, the wheel is "toes in". If the front of the wheel tilts outwardly, the wheel is "toed out".
Control arms, which determine the lateral position of the forward and rear portions of the spindle and thus the toe of the associated wheel, are provided with bushings at either end thereof for accepting a bolt to attach each control arm at one end to the spindle and at the other end to a central portion of the vehicle frame. The attachment hole portions in the spindle and the vehicle frame are of approximately the same diameter as the attachment bolts. The only method of adjusting the toe of a tire in such an arrangement is provided by the "slop" between the bolt receiving holes in the control arm frame and spindle and the diameter of the corresponding attachment bolts. To make toe adjustments in such an assembly, the attachment bolts at the ends of a control arm are loosened while the vehicle is supported on toe adjustment plates. Thereafter, one mechanic moves the wheel laterally to a desired toe position to the extent possible and another mechanic retightens the bolts. A problem with this solution is that due to vibration, etc. of the vehicle during ordinary use, the toe of the vehicle may shift because of lack of positive lateral restraint between the bolts, control arm and the attachment portions of the frame and spindle. Another problem with such an adjustment procedure is that only a relatively small amount of toe adjustment is possible since the amount of "slop" between the bolts and associated holes is usually relatively small. Yet another problem with such an adjustment procedure, is that it requires the service of two mechanics. Still another problem is that it is difficult to measure the toe change until after the operation is completed.
It would be generally desirable to provide a rear toe adjustment assembly enabling a single mechanic to perform an adjustment over a relatively wide range of potential toe changes in a manner which would allow the mechanic to view and measure the toe change as the adjustment is being made, and in a manner which is not subject to shifting due to ordinary vibration, etc. of the vehicle during use.